Search results for "refrigeration"
showing 10 items of 53 documents
A Testing Facility for Refrigerating Plants Equipment Working with New Fluids
2013
A test rig was built in the department of energy, in laboratory of refrigerating engineering for test runs with a lot of fluid and equipment of various kind for commercial refrigeration. The facility has been continuously improved during the past years and allows to perform experiments aiming to assess the performance characteristics both of conventional and new equipment for commercial refrigeration. In the test rig can be tested a lot of cooling loop filled with a secondary fluid for simulation of their behavior in industrial and commercial plants (e.g.: during exploitation in supermarket and hypermarket for refrigeration of foodstuffs in cold store, display cases and cabinets, etc.). The…
Assessing the Robustness of Thermoeconomic Diagnosis of Fouled Evaporators: Sensitivity Analysis of the Exergetic Performance of Direct Expansion Coi…
2016
Thermoeconomic diagnosis of refrigeration systems is a pioneering approach to the diagnosis of malfunctions, which has been recently proven to achieve good performances for the detection of specific faults. Being an exergy-based diagnostic technique, its performance is influenced by the trends of exergy functions in the “design” and “abnormal” conditions. In this paper the sensitivity of performance of thermoeconomic diagnosis in detecting a fouled direct expansion coil and quantifying the additional consumption it induces is investigated; this fault is critical due to the simultaneous air cooling and dehumidification occurring in the coil, that induce variations in both the chemical and th…
SETUP OF VIRTUAL EXPERIMENTS AND CRITICAL ANALYSIS OF CONVENTIONAL THERMOECONOMIC DIAGNOSIS OF MULTIPLE FAULTS IN AIR-CONDENSED ROOFTOP SYSTEMS
2012
The diagnosis of soft faults in vapor compression cooling systems is a crucial activity, since malfunctions may provoke heavy degradation in plant performance and increase the power consumption for space cooling. Among the various Faults Detection and Diagnosis techniques developed over the last two decades, thermoeconomic diagnosis has been playing only a marginal role due to the difficulties encountered when applying the conventional thermoeconomic approaches to vapor compression refrigeration plants. In this paper a critical analysis on capabilities and limits of thermoeconomic diagnosis of refrigeration systems is proposed. The reference plant assumed for this study is a 116 kWc air-con…
Potential applications using LNG cold energy in Sicily
2008
According to previsions, natural gas could be the main energy source worldwide, inducing relevant geopolitical changes. Most likely, such problems will be solved with the development of a gas transportation mode alternative to traditional pipelines: liquefied natural gas (LNG). The global LNG trade has increased rapidly during recent years. A significant amount of energy is consumed to produce low-temperature LNG, which has plenty of cryogenic exergy/ energy. Therefore, the effective utilization of the cryogenic energy associated with LNG vaporization is very important. Sicily, with more than five million inhabitants, is the second biggest region of Italy and in this region will be realized…
PERFORMANCE EVALUATION OF CASCADE REFRIGERATION SYSTEMS USING DIFFERENT REFRIGERANTS
2012
Due to the negative effects of synthetic refrigerants on the environment, natural refrigerants have obtained again interest as alternative refrigerants for different applications because of their zero ODP and negligible GWP. This paper presents a thermodynamic analysis of different two-stage cascade refrigeration systems using as refrigerant carbon dioxide (R744) in low-temperature circuit, and, respectively, ammonia (R717), propane (R290), butane (R600), R404A, R410A and R134a in high-temperature circuit. The operating parameters considered in this study include condensing and evaporating temperatures in high-temperature circuit, temperature difference in the cascade heat exchanger, and e…
Implementation and microbiological stability of dose-banded ganciclovir infusion bags prepared in series by a robotic system.
2018
Objectives The implementation of dose-banding (DB) in centralised, pharmacy-based cytotoxic drug preparation units allows the preparation of standardised doses in series. The aim of this study was to evaluate the feasibility of DB for the prescribing of ganciclovir (GV) infusion solutions and to investigate the microbiological stability of dose-banded, automatically prepared ready-to-administer GV infusion bags by media-fill simulation tests and sterility tests. Methods The frequency of prescription of GV doses was retrospectively analysed before and after implementing the DB scheme. Four dose-ranges or ‘bands’ and the corresponding standard doses (250, 300, 350, 400 mg) were identified. Th…
Thermodynamics of computation and linear stability limits of superfluid refrigeration of a model computing array
2019
We analyze the stability of the temperature profile of an array of computing nanodevices refrigerated by flowing superfluid helium, under variations in temperature, computing rate, and barycentric velocity of helium. It turns out that if the variation in dissipated energy per bit with respect to temperature variations is higher than some critical values, proportional to the effective thermal conductivity of the array, then the steady-state temperature profiles become unstable and refrigeration efficiency is lost. Furthermore, a restriction on the maximum rate of variation in the local computation rate is found.
Single-molecule magnet behavior and magnetocaloric effect in ferromagnetically coupled LnIII-NiII-NiII-LnIII (LnIII = DyIII and GdIII) linear complex…
2014
New types of linear tetranuclear LnIII-NiII-NiII-LnIII (LnIII = Dy (1), Gd (2)) complexes have been prepared using the multidentate ligand N,N′-bis(3-methoxysalicylidene)-1,3-diaminobenzene, which has two sets of NO and OO′ coordination pockets that are able to selectively accommodate NiII and LnIII ions, respectively. The X-ray structure analysis reveals that the NiII ions are bridged by phenylenediimine groups forming a 12-membered metallacycle in the central body of the complex, whereas the LnIII ions are located at both sides of the metallacycle and linked to the NiII ions by diphenoxo bridging groups. Phenylenediimine and diphenoxo bridging groups transmit ferromagnetic exchange intera…
Field-induced slow magnetic relaxation and magnetocaloric effects in an oxalato-bridged gadolinium(iii)-based 2D MOF
2021
The coexistence of field-induced slow magnetic relaxation and moderately large magnetocaloric efficiency in the supra-Kelvin temperature region occurs in the 2D compound [GdIII2(ox)3(H2O)6]n·4nH2O (1), a feature that can be exploited in the proof-of-concept design of a new class of slow-relaxing magnetic materials for cryogenic magnetic refrigeration.
Zeolite-gas systems and solar refrigeration : a study of the adsorptive properties at high pressures in the R22 freon-13X zeolite and ammonia-13X zeo…
1990
The adsorption of ammonia and R22 freon on 13X zeolite was studied in the conditions of possible use of these fluids in heat machines for solar refrigeration. The ranges of temperature and pressure, investigated in this study, extended from 0 to 80 °C and from 10-1 to 6 105 Pa respectively. The adsorption isotherms were collected by microgravimetry using a thermobalance specially built to be used in aggressive gases at pressures up to 106 Pa. Weak hysteresis was detected when ammonia was desorbed below 80 °C. A critical study concerning both applicability of classical adsorption equations (Dubinin-Radushkevitch and Langmuir) and comparison with other zeolite-gas systems is presented. Compar…